>> What other purpose could a one ring hang-up have? <<
The 1-ring scam is well known.
I suspect more people call back than visit 800notes
So, your contention is unproven (as is mine).
However, there is support for my contention ... the FCC warns against the 1-ring scam!
See FAQ #12, at
http://phonehelp.2truth.com/faqs.html
Remember to return here, to 800notes.com, after visiting that site, and let us know if you need additional help.